Week 6: Heart Anatomy and Physiology Flashcards
Where is the heart located?
In the thoracic cavity, medially between the lungs in the space known as the Mediastinum
Where does the Dorsal surface of the heart lie?
Near the bodies of the vertebrae
Where does the Anterior surface of the heart lie?
Deep to the sternum and costal cartilages
When blood is pumped from the right atrium to the right ventricle, it is entering which circuit?
Pulmonary circuit
What is the pulmonary circuit?
It is where blood is low in oxygen but high in CO2
Where does gas exchange occur in the pulmonary circuit?
Gas exchange occurs in the pulmonary capillaries (oxygen into the blood, carbon dioxide out)
When blood is pumped back to the left atrium to the left ventricle, which circuit is it entering?
The systemic circuit
What is the systemic circuit?
It is where oxygen and nutrients are exchanged out of the capillaries and CO2 and wastes are exchanged into them
Which chamber initially receives blood from the systemic circuit?
Right atrium
Blood flow: The Left Atrium flows into the…
Mitral valve (L atrioventricular valve)
Blood flow: The Tricuspid Valve (R atrioventricular valve) flows into the…
Right ventricle
Blood flow: The Right Ventricle flows into the…
Pulmonary semilunar valve (pulmonic valve)
Blood flow: The Pulmonary Vein flows into the…
Left atrium
Blood flow: The Aortic Semilunar Valve flows into the…
Pulmonary vein
Blood flow: The Mitral Valve (L atrioventricular valve) flows into the…
Left ventricle
Blood flow: The Left Ventricle flows into the…
Aortic Semilunar valve (aortic valve)
Blood flow: The Pulmonary Artery flows into the…
Lungs, then to the Right atrium
Blood flow: The Right Atrium flows into the…
Tricuspid valve (R atrioventricular valve)
Blood flow: The Pulmonary Semilunar Valve flows into the…
Pulmonary Artery
What is a Patent Foramen Ovale defect?
An abnormal opening in the interatrial septum, or more commonly, a failure of the foramen ovale to close
What is a Coarctation of the Aorta?
An abnormal narrowing of the aorta
What is a Patent Ductus Arteriosus?
The failure of the ductus arteriosus to close
(Ductus arteriosus allows blood to bypass the lungs in utero)
What is a Tetralogy of Fallot?
An abnormal opening in the interventricular septum
What is the Pericardium/Pericardial Sac?
The membrane that directly surrounds the heart and defines the pericardial cavity
What else does the Pericardium surround?
The major vessels in the areas of closest proximity to the heart
What are the 2 distinct layers of the Pericardium?
Fibrous pericardium & Serous pericardium
What is the Fibrous pericardium?
It is made of tough connective tissue to protect the heart and maintain its position in the thorax
What is the Serous pericardium?
More delicate than the fibrous pericardium, made up of 2 layers (parietal & visceral/epicardium).
What is the Parietal layer of the Serous pericardium fused to?
The fibrous pericardium
What is the Visceral/Epicardium layer of the Serous pericardium fused to?
To the heart and is part of the heart wall
What is the Pericardial cavity filled with?
Lubricating serous fluid
What are Coronary arteries and veins?
Specific arteries and veins supply specific structures of the heart.
Where are Coronary arteries and veins located?
In fat filled groves called Sulcus
What are Sulcus?
The fat filled groves on the surface of the heart that contain Coronary arteries and veins.
What is the Auricle?
It is an extension of an atrium visible on the superior surface of the heart with thin-walled structures that can fill with blood and empty into the atria
How many layers are the walls of the heart made up of?
3
What are the 3 layers of the heart walls?
(superficial to deep)
- Epicardium (outermost)
- Myocardium (middle & thickest)
- Endocardium (innermost)
What is the Epicardium?
The outermost layer of the heart walls
What is the Myocardium?
It is the middle and thickest layer of the heart wall.
What is the Myocardium made up of?
Cardiac muscles cells, also contains blood vessels and nerves that regulate the heart.
What does the Myocardium do?
Contracts to pump blood through the heart and the major arteries.
What is the Endocardium?
The innermost layer of the heart walls that lines the heart chambers and covers heart valves.
What is the Endocardium made up of?
Simple squamous epithelium known as endothelium (continuous with lining of blood vessels)
Do both ventricles (L&R) pump the same amount of blood?
Yes
What is the Lumens?
The region inside each ventricle where the blood is contained.
Which Ventricles Lumen is bigger?
The right because the myocardium is thicker in the left ventricle
Why must the Left Ventricle generated more pressure?
To overcome greater resistance in the systemic circuit
T or F: The pulmonary circuit is shorter and has less resistance.
True
What is the Septum?
It divides the heart into chambers (plural = Septa)
What do the Pulmonary Trunk and Aorta cover?
The Interatrial Septum
What are Interatrial Septa?
Septum between the atria
What are Interventricular Septa?
Septum between the ventricles
What are Atrioventricular Septa?
Septum between the atria and ventricles
What do the Heart Valves do?
Allows one way flow of blood
How many valves are in the heart?
4
What are the names of the 4 heart valves?
Tricuspid
Mitral
Aortic
Pulmonary
What is the Tricuspid valve?
R atrioventricular
What is the Mitral valve?
L atrioventricular
What is the Aortic valve?
Aortic semilunar
What is the Pulmonary valve?
Pulmonic semilunar
The ventricles of the heart are separated into right and left sides by the…
Interventricular Septum
The thin layer of tissue lining the interior of the heart chambers is called the…
Endocardium
What are the 4 structures of the Right Artium?
Superior Vena Cava
Inferior Vena Cava
Coronary Sinus
What is the Superior Vena Cava?
It drains blood from regions superior to the diaphragm (the head, neck, upper limbs, and the thoracic region), then empties into the superior and posterior portions of the right atrium
What is the Inferior Vena Cava?
Drains blood from areas inferior to the diaphragm (the lower limbs and abdominopelvic region) of the body, then empties into the posterior portion of the atria, but inferior to the opening of the superior vena cava
What is the Coronary Sinus?
Drains most of the coronary veins that return systemic blood from the heart
What does the Atria receive on a continuous basis?
Venous blood
What does the Atria do?
It contracts to actively pump blood into the ventricles just before ventricular contraction
What happens to the Semilunar Valves when the Atrioventricular Valves are open?
They close to allow for ventricular filling and to prevent backfilling
What are Chordae tendineae known as?
The heart strings
What are Chordae tendineae?
They are extensions of the myocardium that attach to the valves of the heart to prevent the valves from being blown back into the atria
What is the Cardiac Skeleton?
Connective tissue that reinforces the septum around valves, four rings that act at the point of attachment for the heart valves.
Also provides an important boundary in the heart electrical conduction system.
What is Valvular dysfunction?
It results in disrupted blood flow= valvular insufficiency
What is a Vascular Prolapse?
The valve cusp forced backward by force of blood due to damaged/broken chordae tendineae
What is Stenosis?
Heart valve rigidity/calcification that over time weakens the heart
List the valves in the order that the blood flows from the vena cava through the heart?
Tricuspid
Pulmonary semilunar
Bicuspid
Aortic semilunar
TPBA
Why do the Cardiac muscle cells require circulation?
To supply oxygen and nutrients and remove wastes to manage its continuous activity
What are the L&R Coronary Arteries?
The first to branch off the aorta and arise from two of the three sinuses located near the base of the aorta and are generally located in the sulci
What are Epicardial coronary arteries?
Coronary vessel branches that remain on the surface of the artery and follow the sulci
What do Cardiac veins parallel?
The small cardiac arteries
What do Cardiac veins drain into?
The Coronary Sinus
What is an Anastomosis?
Area where vessels unite to form interconnections that allow blood to circulate to a region even if there may be partial blockage in another branch
What is a Myocardial infarction (MI)/Heart Attack?
Normally results from a lack of blood flow (ischemia) and oxygen (hypoxia) to a region of the heart due to restricted blood flow, resulting in death of the cardiac muscle cells
What are the 2 branches of the Left (main) Coronary Artery?
The circumflex artery and the Anterior Interventricular Artery/Anterior Descending Artery
Left Coronary Artery: What is the Circumflex Artery?
It arises from the left coronary artery and follows the coronary sulcus to the left, then fuses with the small branches of the right coronary artery
What does the Left (main) Coronary Artery follow?
Follows the anterior interventricular sulcus around the pulmonary trunk, then gives rise to numerous smaller branches (diagonal branches) that interconnect with the branches of the posterior interventricular artery, forming anastomoses
What is the Right Coronary Artery?
Distributes blood to the right atrium, portions of both ventricles, and the heart conduction system
What arises from the Right Coronary Artery?
One or more marginal arteries arise from the right coronary artery inferior to the right atrium, and the Posterior Interventricular Artery/Posterior Descending Artery
What do marginal arteries do?
Supply blood to the superficial portions of the right ventricle
What do Coronary Arteries do?
Drain the heart and generally parallel the large surface arteries
Where does the Great Cardiac Vein drain to?
It follows the interventricular sulcus, eventually flowing into the coronary sulcus into the coronary sinus on the posterior surface (into right atrium)
drains areas supplied by the anterior interventricular artery (LAD)
Where does the Anterior Cardiac Veins drain to?
Found parallel the small cardiac arteries and drain the anterior surface of the right ventricle; unlike these other cardiac veins, it bypasses the coronary sinus and drains directly into the right atrium.
What major branches does the Great Cardiac vein receive?
Posterior cardiac vein
Middle cardiac vein
Small cardiac vein
Where does the Anterior Cardiac Veins drain to?
What does it mean that Cardiac Muscle cells are Autorhythmic?
They are able to initiate electrical potential at a fixed rate which rapidly spreads from cell-cell to trigger contraction
What is heart rate modulated by?
The endocrine and nervous system
What are the two types of Major Cardiac Muscle Cells?
- Myocardial Contractile Cells
- Myocardial Conducting Cells
What are Myocardial Contractile Cells?
99% cells in atria/ventricles, conduct impulses responsible for muscle contraction to pump blood
What are Myocardial Conducting Cells?
1% of cells, form conduction system of heart, smaller than contractile cells, initiate/propagate action potential (electrical impulse) triggering contraction to pump blood
What 3 things are found in Cardiac Muscle cells?
Intercalated discs
Desmosomes
Gap Junctions
What are Intercalated Discs?
Junction between 2 adjoining muscle cells that helps support the synchronized contraction of the muscle
What are Gap Junctions?
They allow movement of ions (Na/K/Ca) across cell membranes-this movement creates a depolarizing current, aiding electrical conduction.
What type of contractions do cardiac muscles cells undergo?
Twitch-type contractions (they are unable to respond to another stimulus)
Why do cardiac muscle cells undergo a long refractory period and brief relaxation periods?
So the heart can fill with blood for the next cycle
Why is the refractory period long?
To prevent the possibility of tetany
What is Tetany?
A condition in which the muscle remains involuntarily contracted which prevents the heart from pumping blood
What is the rate of the cardiac muscle’s rhythm controlled by?
Autonomic nerve signals and the heart’s conduction system
What sets the contraction rate for the cardiac muscle cells?
The cell with the fastest contraction rate
What are the key areas of the Conduction system?
- Sinoatrial (SA) node
- Atrioventricular (AV) node
- Internodal pathways
- Bachmann’s bundle
- AV bundle (Bundle of His)
- Right and left bundle branches
- Purkinje fibers
What is the SA node?
Normal electrical pattern of the hear is the sinus rhythm, the pacemaker of the heart.
Where does the SA node’s impulse go?
SA node impulse travels atria via internodal pathways to the myocardial contractile cells, to the AV node
What are the 3 Internodal pathways?
Anterior (Bachmann’s bundle-direct path to AV node), middle, and posterior leading to the AV node
What is the AV node?
Located in the inferior portion of the right atrium within the atrioventricular septum, the septum prevents the impulse from spreading directly to the ventricles without passing through the AV node.
What is a Critical Pause?
here is a critical pause before the AV node depolarizes and transmits the impulse to the atrioventricular bundle that allows the atrial cardiomyocytes to complete their contraction that pumps blood into the ventricles before the impulse is transmitted to the cells of the ventricle itself
What is the cycle of the Cardiac Conduction?
- The sinoatrial (SA) node and the remainder of the conduction system are at rest
- The SA node initiates the action potential, which sweeps across the atria
- After reaching the atrioventricular node, there is a delay of approximately 100 ms that allows the atria to complete pumping blood before the impulse is transmitted to the atrioventricular bundle
- Following the delay, the impulse travels through the atrioventricular bundle (Bundle of His) and bundle branches to the Purkinje fibers and also reaches the right papillary muscle via the moderator band
- The impulse spreads to the contractile fibers of the ventricle
- Ventricular contraction begins
What does the series of Na+ ion channels of Conductive cells allow for?
For slow influx of Na+ causing membrane potential to rise (from -60mV up to -40mV)
What does the movement of Na+ initiate?
Spontaneous (prepotential) depolarization
What does Spontaneous depolarization trigger?
This triggers Ca+2 ion channels to open, Ca+2 rapidly enters cell until cell reaches +15mV.
What happens after Depolarization?
At this point, Ca+2 channels close, K+ ion channel open and K+ moves out of cell (repolarization), decreasing membrane potential
When does a new cycle begin?
When membrane potential reaches -60mV, K+ ion channels close and Na+ channel re-opens
What type of electrical pattern do Contractile cells follow?
Rapid depolarization (3-5ms), plateau phase (175ms), repolarization (75ms); Long refractory periods
What sort of Heart Rate does the SA node initiate?
The SA node (pacemaker of the heart), initiates a heart impulse approximately 80–100 times per minute (reaches electrical threshold faster)
Without the SA node, what sort of Heart Rate would the AV node generate?
40-60 beats per minute
What sort of heart rate would the Atrioventricular bundle (Bundle of His) generate if the AV node was blocked?
30-40 beats per minute
What sort of heart rate would the bundle branches and Purkinje fibres generate if the AV node was blocked?
Bundle branches = 20-30 beats per minute
Purkinje fibres = 15-20 beats per minute
What is an Electrocardiogram (ECG)?
Careful placement of surface electrodes on the body can capture the electrical signals of the heart
What are the 5 prominent points on the ECG?
P wave
QRS complex
T wave
What is the P wave show?
Depolarization of the atria
What does the QRS complex show?
Depolarization of the ventricles
(Depolarization of the atria is hidden here as well)
What does the T wave show?
Repolarization of the ventricles
What is a Cardiac Cycle?
Each complete heart beat is called a cardiac cycle and includes the contraction and relaxation of the atria and ventricles
When does a Cardiac Cycle begin and end?
The period of time that begins with contraction of the atria and ends with ventricular relaxation
How long is a Cardiac Cycle?
Each cycle takes about 0.8 seconds to complete if the heart is beating at 72 beats per minute
What is Systole?
The period of contraction that the heart undergoes while it pumps blood into circulation
What is Diastole?
The period of relaxation that occurs as the chambers fill with blood
Do the Atria and the Ventricles both undergo systole and diastole?
Yes
Where does fluid flow due to the pressure gradient?
From regions of high to low pressure
How long does Atrial systole last?
~100ms and it ends prior to ventricular systole
What are the 2 phases of Ventricle Systole?
- Isovolumetric contraction
- Ventricular Ejection Phase
What is Phase 1: Isovolumetric Contraction?
Initial phase of ventricular systole where pressure in ventricles increases but not enough to open the semilunar
What is Phase 2: Ventricular Ejection Phase?
Ventricular contraction has
raised ventricular pressure that is greater than pressure in the
pulmonary trunk/aorta, and blood is pumped forward (approx. 70-80mls=stroke volume)
The contraction of the heart is called…
Systole
The relaxation of the heart is called…
Diastole
What noise are made by the closing of the valves?
Lub-Dub/S1 & S2
What are the 2 healthy heart sounds?
S1 & S2
What is the sound S1?
“Lub” - the closing of the atrioventricular valves during ventricular systole
What is the sound S2?
“Dub” - the closing of the semilunar valves during ventricular diastole
What are the other 2 heart sounds you don’t want to hear?
S3 & S4
What is the sound S3?
Is rarely heard in healthy individuals, typically heard in heart failure.
- Slosh-ing-in OR Ken-tuck-y (S1,S2,S3).
What is the sound S4?
It is the sound of the contraction of the atria pushing blood into a stiff or hypertrophic ventricle.
- A-Stiff-Wall OR Ten-nes-see (S4,S1,S2)
What pattern do you listen to the valves in?
A Z pattern, first with diaphragm, then with the bell.
What intercostal spaces are the valves found in?
2-2-3-5-5
The first heart sound represents which portion of the cardiac cycle?
The closing of the atrioventricular valves
What is Heart Rate (HR)?
Number of beats per mintute
What is Stroke Volume (SV)?
Volume of blood ejected from EACH ventricle during each beat
What is Cardiac Output (CO)?
Volume of blood pumped by EACH ventricle in ONE MINUTE
What are some factors affecting Heart Rate (HR)?
Autonomic innervation
Hormones
Fitness levels
Age
What are some factors affecting Stroke Volume (SV)?
Heart size
Fitness levels
Gender
Contractility
Duration of contraction
Preload (EDV)
Afterload (resistance)
How do you calculate Stroke Volume (SV)?
SV = Preload (EDV) - Afterload (ESV)
How do you calculate Cardiac Output (CO)?
CO = HR x SV
Nervous control over heart rate is centralized within two paired cardiovascular centres of what part of the brain?
Medulla oblongata
What are Cardioaccelerator centres?
Stimulate heart activity via sympathetic stimulation of the
cardioaccelerator nerves
What are Cardioinhibitory centers?
Decrease heart activity via parasympathetic stimulation as one component of the vagus nerve (cranial nerve X)
Both sympathetic and parasympathetic stimulations flow through a paired
complex network of nerve fibers known as what, located near the base of the heart?
The Cardiac Plexus
What is the role of Norepinephrine?
Sympathetic stimulation, increase the HR
What is the role of Acetylcholine?
Parasympathetic stimulation, slows the HR
What are Cardiac Reflexes?
Series of autonomic reflexes that enable the cardiovascular centers to regulate heart function based upon
sensory information from a variety of visceral sensors
What are the 4 cardiac receptors?
- Proprioreceptors
- Baroreceptors
- Chemoreceptors
- Limbic system
What is Preload?
Amount of blood in the ventricles at the end of atrial systole just prior to ventricular contraction
What is Starling’s law?
Force of contraction proportional to initial length of
muscle fiber, greater the stretch, greater the contraction, greater the stroke volume
What is Contractility?
Force of contraction of the heart muscle, influenced by positive/negative inotropic factors
What is Afterload?
Force the ventricles must develop to effectively
pump blood against the resistance in the vessels
What is Organogenesis?
The formation of new organs
What is Histogenesis?
The formation of new tissues
What organ forms first in a fetus?
The heart
Genesis occurs in what 3 layers?
Ectoderm (outer layer)
Mesoderm (middle layer)
Endoderm (inner layer)
What happens during days 18-19 of heart formation?
Heart originates from the mesoderm
What happens during days 21-22 of heart formation?
Heart begins beating regularly and pumping blood
What are endocardial tubes?
A pair of strands called cardiogenic cords that form a hollow lumen, they then fuse into a single heart tube and differentiate into structures.
What happens during days 23-28 of heart formation?
Primitive heart begins to form an S-shape within the pericardium, internal septa begin to form separating the atria and ventricles.
What happens during weeks 5-8 of heart formation?
AV valves form
What happens during weeks 5-9 of heart formation?
Semilunar valves form
What is the Foramen ovale?
The foramen ovale allows blood in the fetal heart to pass directly from the right atrium
to the left atrium, allowing some blood to bypass the pulmonary circuit.
What is the Septum Primum?
a flap of tissue that
previously acted as a valve that closes the foramen ovale and establishes the typical cardiac circulation pattern seconds after birth.
